A Precision Measurement of the Top Quark Mass

Thesis/Dissertation · Sat Jan 01 00:00:00 EST 2005

DOI:https://doi.org/10.2172/15017235· OSTI ID:15017235

Black, Kevin Matthew ^[1]

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1. Boston Univ., MA (United States)

This dissertation describes the measurement of the top quark mass using events recorded during a ~ 230 pb^-1 exposure of the D0 detector to proton-anti-proton (p$$\bar{p}$$) collisions at a center of mass energy of 1.96 TeV. The Standard Model of particle physics predicts that the top quark will decay into a bottom quark and a W boson close to 100% of the time. The bottom quark will hadronize (bind with another quark) and produce a jet of hadronic particles. The W bosons can decay either into a charged lepton and a neutrino or a pair of quarks. this dissertation focuses on the top quark (t$$\bar{t}$$) events in which one W decays hadronically and the other decays leptonically. Two methods of identifying t$$\bar{t}$$ events from the large number of events produced are used. The first is based on the unique topology of the final state particles of a heavy particle. By using the topological information of the event, the t$$\bar{t}$$ events can be efficiently extracted from the background. The second method relies on the identification of the remnants of the long lived bottom quarks that are expected to be produced in the decay of almost every top quark. Because the largest background processes do not contain bottom quarks, this is an extremely efficient way to select the events retaining about 60% of the t$$\bar{t}$$ events and removing almost 90% of the background. A kinematic fit to the top quark mass is performed on the t$$\bar{t}$$ candidate events using the final state particles that are seen in the detector. A likelihood technique is then used to extract the most likely value of the top quark mass, m_t, and signal fraction. The result for the topological selection is m_t = 169.9 ± 5.8(statistical)$$+8.0\atop{-7.8}$$(systematic) GeV while the results on the sample selected from identification of a b quark in the event is m_t = 170.6 ± 4.2(statistical)$$+6.3\atop{-6.8}$$(systematic) GeV.

• Research Organization: Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76CH03000
• OSTI ID: 15017235
• Report Number(s): FERMILAB-THESIS-2005-08; TRN: US200612%%658
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
A CENTERS
ACCURACY
B QUARKS
DECAY
INTERMEDIATE BOSONS
LEPTONS
NEUTRINOS
PHYSICS
QUARKS
STANDARD MODEL
T QUARKS
TOPOLOGY
Experiment-HEP